Fig. 1. Aspects of planar cell polarity. (A) In a wild-type eye, ommatidia are rotated uniformly above and below the dorsoventral equator. (B) Localization of the polarity cue. In wild-type wing cells, Fz is localized to the distal sides of cells, whereas Fmi is localized to both the proximal and distal sides of cells. (C) The basic PCP pathway that determines wing hair polarity. (D) Classes of PCP defects in the wing epithelium. In wild type, a single hair is secreted from the distal-most vertex of each cell. Mutations of the PCP core group genes (fz, fmi/stan, dsh, pk and vang/stmb) cause hairs to project from central locations and to have a non-distal orientation. RhoA and Rok mutants show multiple wing hairs projected from the distal side of a cell. The tsr mutants show a single wing hair that is projected in a non-distal orientation and is not centered through the distal-most vertex of a cell.